riding mower wont start

Riding Mower Won’t Start (Why + How To Fix)

It’s a sunny day, you’ve got a bit of spare time so you think I’ll mow the lawn. But when you come to use your machine, you find that your riding lawn mower won’t start. Is there anything more frustrating?

But before you throw in the towel, why not take a few moments to figure out why you’re having riding lawn mower starting problems? There could be several reasons this is happening and in this guide, we’ll take a look at some of the most common issues and how to fix them.

No Gas In The Fuel Tank

Before you start looking at more complex potential issues, it’s worth making sure that there is some gas in the fuel tank. While worrying that your riding mower may have a serious problem, you may omit to think about the more obvious solutions.

How To Fix It

Add some gas to the tank

Wrong Or Old Gas In The Fuel Tank

When it comes to buying fuel for your riding lawn mower, you certainly have a lot of options. But the problem is that not all types of fuel are suitable for all lawn mowers so it’s vital that you choose the right one or you may end up with riding mower starting problems.

Generally speaking, your riding lawn mower needs unleaded 87 octane gas with no more than 10% ethanol. Look out for E10 or Regular fuel. Also make sure to check your owner’s guide and the information on the fuel pump to ensure you’re putting the right gas into your mower.

Old fuel can start to evaporate when left in the fuel tank for long periods of time and this can result in corrosion, sticky residue and starting problems. It’s a good idea to avoid leaving fuel in the tank for any longer than 30 days if you don’t plan on using the riding mower.

How To Fix It

Always double check that you are using the correct fuel. If you’re not, you’ll need to drain the fuel tank and fill it with an appropriate batch of fresh fuel.

When you plan on leaving the mower out of use for some time, drain the fuel tank to avoid problems with clogging of fuel filters and other parts of your riding mower.

Choke Fault

A riding lawn mower usually has a manual choke but on a lot of the more modern models, you may have an auto choke. In the case of manual choke, this may be on the wrong setting which will prevent the riding mower from firing up.

How To Fix It

If an auto choke fails then you will need to have this replaced. However, if your mower has a manual choke, make sure that it is set to full when you are trying to start a cold mower engine.

Plugged Up Fuel Filter

Your fuel filter needs to be clear so that the gas can pass through. If it is dirty or clogged then this cannot happen and the fuel simply won’t get to the engine in order for the mower to start. What’s more, if the fuel filter is not clean, debris and particles can get into the engine which will only lead to further problems.

How To Fix It

Get into the habit of regularly replacing your fuel filter. Doing this around once per mowing season should be enough but it’s important to also get into the habit of checking it to make sure it isn’t clogged. If it is, then you will need to replace it early. Fortunately, these parts are incredibly affordable.

Air Filter Is Blocked

As well as fuel, a riding lawn mower engine needs air if it’s going to start. But this cannot be delivered to the engine when the air filter is blocked and this can and will happen thanks to debris and dirt. So, it’s important to keep a close eye on your air filters and make sure that they don’t become clogged.

If you ignore this problem as it gets worse, it can lead to serious engine damage. What’s more, when the engine is starved of air, there’s a higher risk of it overheating, in which case, it’ll just shut off anyway. By staying on top of air filter maintenance, you can eradicate the risk of more complex engine issues.

air filter is blocked - riding mower

How To Fix It

If you have a blocked or dirty air filter then it’s pretty easy to clean. You can remove it from its housing and firmly tap it against a solid surface. This should remove most of the dirt and debris. While it might appear that it would make the job easier, it is not recommended to use an air compressor to clean your air filter.

Before you put the air filter back into your riding mower, take a moment to hold it up to the light to check that it’s properly clean. If it is, you should see light shining through. If not, this tells you that the filter needs to be replaced.

Damaged Or Dirty Spark Plug

Riding lawn mowers have either one of two spark plugs and sometimes the connections on these can loosen which will cause problems with your lawn mower getting started.

Just like other parts of your lawn mower, your spark plugs may become dirty and the most common cause for this is a build up of carbon. When this happens, the spark plugs don’t perform properly and your lawn mower won’t fire up.

How To Fix It

Take the spark plug(s) out of your riding mower and check it for any signs of dirt or carbon. You should also look at the porcelain insulators as these can become cracked which means that you will need to get a new spark plug. In some cases, the spark plug can be cleaned but usually, they’ll need replacing.

Also make sure that the wires are not loose and that the spark plugs are gapped correctly.

Control Module

Pretty much all modern riding mowers will be fitted with a control module. These are designed to work with the safety sensors and will start and stop the mower on command. Yours might be integrated into the dash but many are just very simple printed circuits.

There are, of course, some lawn mowers that don’t have a control module. In this case, it’s the ignition switch that does the same job.

From time to time, these modules can fail especially if they are exposed to a lot of moisture. Moreover, the wiring within the system can fail. For mowers that don’t have a control module you are at something of an advantage as it’s usually a lot easier to diagnose problems.

How To Fix It

You can test the control module using a spark tester and this will tell you whether there is a problem with the coil or the stop switch. However, in most cases, if there is a problem, it’s something that needs to be dealt with by a professional so you will have to take your lawn mower in for repair.

The good news is that these control modules are powered by electricity and so, are one of the most reliable parts of your riding mower’s engine and very rarely suffer with issues.

Blocked Or Dirty Carburetor

Just like other parts of your lawn mower, the carburetor can become dirty or blocked when old fuel is left in the tank. But this part can also clog up as you use the mower so it’s something you need to keep an eye on during your routine mower maintenance.

The carburetor is designed to regulate the air and fuel mixture in order that combustion can take place. If it is dirty or blocked, it won’t perform as it should and your riding mower may struggle to get going.

blocked or dirty carburetor - riding mower

How To Fix It

Cleaning your carburetor is simple especially when you consider that you can buy sprayable carb cleaner that is usually more than enough to get the job done. Make sure to take the carburetor apart so that it gets a good clean.

Where the carburetor is dirty beyond repair, you may need to replace it. If you’re not confident in doing this then be sure to take your riding mower to a professional.

Bad Safety Switch

Riding lawn mowers are fitted with a safety switch and this is for your own good. There is one safety switch located underneath the mower’s seat that switches off the deck if you are not in the seat. Sensors tell the mower whether the operator is present.

There’s another safety that stops the lawn mower from starting if the parking brake isn’t engaged. Some lawn mowers will have other safety features but you’ll need to check your owner’s manual to see what your machine is fitted with. In any case, if safety switches fail, this could stop the mower from firing up.

How To Fix It

To determine whether the safety switch is a problem, you will need to use a multimeter to test it. Do not try to bypass the safety switch if it is faulty as this could be incredibly dangerous. 

Dead or Bad Battery

If your riding lawn has loose cables, corrosion on the battery terminals or any other battery related issues, you’re going to have a very hard time starting it up. You’ll need to take a close look at the battery and its components to determine if this is the cause of the problem.

How To Fix It

If there is corrosion on the terminals then this can be removed using a cleaning solution of baking soda and water. You can apply this and work it in using a wire brush which should be enough to get rid of the corrosion. Make sure that everything is dry before you try to operate the mower again.

You might also need to use a multimeter to test the battery function. In some cases, the charge may have dropped and if this falls below 12 volts, you’ll need to give it a boost in order for it to have enough power to get the battery started. In the event that the battery no longer holds its charge, it will need to be replaced.

dead or bad battery - riding mower

Faulty Charging System

If you have a weak battery this might be a result of a faulty charging system. Although it’s unlikely that this is the main source of the starting problems, it’s likely not helping.

If the charging system isn’t giving the battery enough of a boost, the battery won’t provide enough power to start the mower. Usually, this will be related to the alternator although there may be other issues at play.

How To Fix It

Sorting out your charging system isn’t usually something that can be done at home so it’s best to take your riding lawn mower into the shop and have a pro look at it.

If you do try to fix it at home, you can end up replacing a whole host of parts to no avail and all you’ll achieve is putting a big dent in your bank balance.

Bad Starter Solenoid

The solenoid is an electromagnetic switch on your lawn mower which gets the starter motor going. When you turn the ignition key, listen out for either a humming or clicking sound as this will tell you that there’s likely an issue with the starter solenoid. You may also notice smoke when trying to start the mower.

How To Fix It

If the starter solenoid is faulty, it will need to be replaced.

Bad Ignition Switch

Try inserting and turning the ignition key; does something feel off or does the mower just not start at all? If so, then the problem could be with the ignition switch but to determine this, you will need to run a diagnostic test.

How To Fix It

It’s time for your multimeter to shine again and this will tell you whether there are any problems with the ignition switch. If there is an issue, you will need to replace the ignition switch. This is also a good time to check that there aren’t any problems with the spark plug.

Blown Fuse

Your riding lawn mower will be fitted with a fuse and its job is to protect the electrical systems within the mower. Sometimes, this fuse can blow and this means that the lawn mower won’t start. You’ll need to check the fuse to determine if it has blown but make sure to consult your owner’s manual as where the fuse is located will differ depending on the model.

However, in a lot of cases, the fuse will be located somewhere near the battery so this is a good first place to check. In other cases, the fuse may be installed behind the dash.

blown fuse - riding mower

How To Fix It

Once you have located the fuse and seen that it has blown, you will need to replace it. However, if you find that the fuse continues to blow then this could signal that there is a more deeply-rooted problem. To assess this, you’ll likely need to take your lawn mower to a repair shop.

Riding Lawn Mower Won’t Turn Over

If your riding lawn mower won’t turn over then there is likely a problem with either the gas, spark or compression.

You need to make sure that you are using the right type of fuel for your riding mower. Some manufacturers will suggest using an ethanol based fuel while others recommend regular fuel. It’s important to adhere to this as the manufacturer is suggesting what works well with that particular engine.

To get going, your riding mower engine also needs air but this can be inhibited when the air filters are dirty so make sure to check these if your riding lawn mower won’t turn over.

Finally, you need to make sure that the engine can build up enough internal pressure to start and this can be tested using a compression tester. Although with modern riding mowers, there’s almost always a compression release mechanism which should make the mower easier to start.

Riding Lawn Mower Clicks But Won’t Start

If your riding lawn mower clicks but won’t start then the most common cause of this is a bad starter solenoid. That said, it’s also just as likely that there may be a wiring issue or a problem with the starter motor.

Your modern riding mower will have a safety sensor, known as a lock out which will activate when the correct operating process isn’t followed. In this case, the engine will be prevented from starting so it’s worth checking that you’re following the right procedure.

Riding Lawn Mower Is Smoking

A riding lawn mower that is producing smoke could have some internal engine issues which may be serious and need to be addressed by a professional.

But for the most part, smoke will be caused by oil burning on a hot surface or because of something as easily fixable as a blocked air filter. You may also experience problems with a smoking riding lawn mower if the oil level is incorrect so be sure to check this as well.

Riding Lawn Mower Troubleshooting: When To See A Professional

Most of the things we have discussed in this guide are easily fixable at home. However, if you are ever unsure about how to diagnose or fix a problem with your riding lawn mower then it’s best to enlist the help of a professional.

Trying to address a problem that you’re not confident in fixing could result in you doing more harm than good to your riding lawn mower. What’s more, in many situations, you can end up voiding your warranty when trying to tackle an issue you aren’t qualified to handle.

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Andrew Fisher

Andrew Fisher

Andrew is a dedicated father of three who really takes pride in his lawn and garden. You'll find Andrew behind the scenes of almost everything Edge Your Lawn produces. When he's not helping readers find all the information they need, he's in his backyard working on his lawn and garden landscaping. This year he hopes to build an outdoor deck and sort out his veg patches.